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Journal of Membrane Biology

, Volume 235, Issue 2, pp 73–87 | Cite as

Characterization of the Rapidly Activating Delayed Rectifier Potassium Current, I Kr, in HL-1 Mouse Atrial Myocytes

  • Futoshi Toyoda
  • Wei-Guang Ding
  • Dimitar P. Zankov
  • Mariko Omatsu-Kanbe
  • Takahiro Isono
  • Minoru Horie
  • Hiroshi Matsuura
Article

Abstract

HL-1 is the adult murine cardiac cell line that can be passaged repeatedly in vitro without losing differentiated phenotype. The present study was designed to characterize the rapidly activating delayed rectifier potassium current, I Kr, endogenously expressed in HL-1 cells using the whole-cell patch-clamp technique. In the presence of nisoldipine, depolarizing voltage steps applied from a holding potential of −50 mV evoked the time-dependent outward current, followed by slowly decaying outward tail current upon return to the holding potential. The amplitude of the current increased with depolarizations up to 0 mV but then progressively decreased with further depolarizations. The time-dependent outward current as well as the tail current were highly sensitive to block by E-4031 and dofetilide (IC50 of 21.1 and 15.1 nM, respectively) and almost totally abolished by micromolar concentrations of each drug, suggesting that most of the outward current in HL-1 cells was attributable to I Kr. The magnitude of I Kr available from HL-1 cells (18.1 ± 1.5 pA pF−1) was sufficient for reliable measurements of various gating parameters. RT-PCR and Western blot analysis revealed the expression of alternatively spliced forms of mouse ether-a-go-go-related genes (mERG1), the full-length mERG1a and the N-terminally truncated mERG1b isoforms. Knockdown of mERG1 transcripts with small interfering RNA (siRNA) dramatically reduced I Kr amplitude, confirming the molecular link of mERG1 and I Kr in HL-1 cells. These findings demonstrate that HL-1 cells possess I Kr with properties comparable to those in native cardiac I Kr and provide an experimental model suitable for studies of I Kr channels.

Keywords

Cardiac cell line Potassium current Potassium channel Patch-clamp HL-1 cell siRNA 

Notes

Acknowledgements

This study was supported by a Grant-in Aid for Scientific Research from the Japan Society for the Promotion of Science. We are grateful to Dr. W. C. Claycomb for providing HL-1 cells.

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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Futoshi Toyoda
    • 1
  • Wei-Guang Ding
    • 1
  • Dimitar P. Zankov
    • 1
    • 2
  • Mariko Omatsu-Kanbe
    • 1
  • Takahiro Isono
    • 3
  • Minoru Horie
    • 2
  • Hiroshi Matsuura
    • 1
  1. 1.Department of PhysiologyShiga University of Medical ScienceOtsuJapan
  2. 2.Department of Cardiovascular and Respiratory MedicineShiga University of Medical ScienceOtsuJapan
  3. 3.Central Research LaboratoryShiga University of Medical ScienceOtsuJapan

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